|Publication number||US8231771 B2|
|Application number||US 11/849,169|
|Publication date||Jul 31, 2012|
|Filing date||Aug 31, 2007|
|Priority date||Aug 31, 2007|
|Also published as||US20090056623|
|Publication number||11849169, 849169, US 8231771 B2, US 8231771B2, US-B2-8231771, US8231771 B2, US8231771B2|
|Inventors||Carmen Crowley, Thomas H. Croyle, Todd Fitz, James Paul Ryan, Masahiro Ishikawa|
|Original Assignee||Honda Motor Co., Ltd.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (15), Classifications (12), Legal Events (1)|
|External Links: USPTO, USPTO Assignment, Espacenet|
The disclosed subject matter relates to devices and methods for coating of conductive plastic and other types of parts. More particularly, the disclosed subject matter relates to connecting and grounding mechanisms and associated methods for use with conductive plastic parts that are to be electromotively coated.
2. Brief Description of the Related Art
The term “electromotive” coating process as used herein refers to any coating process in which an electrical potential exists between the part being coated and the coating material. Examples of electromotive coating processes include electrostatic coating, electrodeposition (“e-coat”) processes, electromotive vapor deposition, and electroplating processes. The part may be painted or coated with any suitable water-based or organic-based composition (or water/organic mixture) including conductive primer compositions which further enhance the electronic conductivity of the article, or with a solventless organic composition by a powder coating or vapor deposition method.
In electrostatic coating, the coating or fluid (e.g., paint) is typically atomized, then negatively charged. The part to be coated is electrically neutral, making the part positive with respect to the negative coating droplets. Thus, the coating particles are attracted to the surface of the part and held there by the charge differential until cured.
When an electrostatic spray gun is used, droplets of fluid/paint pick up a charge from an electrically charged electrode located on the gun (usually at the tip of the spray nozzle of the gun). The charged droplets are discharged from the gun by a combination of fluid pressure and air pressure.
Electrostatic spraying offers high transfer efficiency and excellent edge coverage. The attraction between charged paint or fluid droplets and the part can be strong enough to cause paint overspray to curve back and adhere to the part, which results in more efficient and consistent coating.
Electrodeposition (e-coat) techniques are also known in the art. In general, organic coatings can be applied to conductive substrates such as metals or conductive plastics by electrodeposition. An aqueous media containing the organic coating to be applied is formed and is commonly referred to as an e-coat bath. The aqueous media typically contains from about 5% to about 30% solids.
An organic polymer is dispersed throughout the e-coat bath and may be positively or negatively charged. Coating of the part is accomplished by immersing the part in the aqueous media and applying a current to the part. The charged polymers are attracted to the material (part) to be coated, which has the opposite charge. The organic particles are then deposited onto the part where they coalesce forming a coating. The part is removed from the e-coat bath rinsed, and the coating is cured. Curing the organic coating to form a final film aids in making the coating tough, resistant to water and organic solvents, etc.
Electrophoretic deposition systems are characterized as either anodic or cathodic thereby indicating the function of the part to be coated. Where the part to be coated is the cathode, the system is referred to as a cathodic system. Similarly, where the part to be coated is the anode, the system is referred to as an anodic system.
Drawbacks with electromotive systems relate to the ability to maintain the part, and especially conductive plastic parts, at a particular electrical potential. In addition, certain problems can arise when intermittent or unwanted electrical or mechanical connections between any of the components of the coating system occur. For example, unwanted discharge of electrical potential can occur and variations in the electrical field during the coating process can occur due to the unwanted contact, or inadequate connection, which can lead to both quality and safety problems.
A drawback unique to electrostatic applications is that the process may not efficiently coat recessed areas due to what is known as Faraday cages (the charged droplets tend to be attracted to the sides of the recess and sharp edges instead of penetrating to the bottom). In addition, electrically conductive materials that are located near the spray area, such as the supply mechanisms, containers, and spray equipment should be grounded to prevent static buildup, to prevent unwanted electrical discharge, and to provide a quality coating. All mechanisms that carry or hold the parts should be kept clean to ensure conductivity to ground. Charges that build up on ungrounded surfaces may discharge or cause inefficient or deficient coating results. Thus there has been a long felt need in the art to provide consistent and positive connection between the part that is being coated and the carrying or holding mechanisms.
In some typical coating systems, parts to be coated are transported through a coating zone or bath by a mechanical conveyor. The parts can be constructed of a conductive material such as metal or conductive plastics. The conveyor can be made from similar materials and should be maintained at or near the potential of the part to be coated which, at least for some electrostatic processes, can be at the electrical ground potential. The parts to be coated are supported on the conveyor by hangars which maintain the parts close together and at the potential of the conveyor. The coating dispensing device can be a gun, as described above for electrostatic processes, or can be another type of spray nozzle, and includes a mechanism for electrically charging the dispensed particles of coating material to a relatively high potential, typically a high negative potential, with respect to the potential of the conveyor and hangars. Alternatively, the coating dispensing device can be a bath into which the hangars direct the part to be coated.
Intermittent contact or high-impedance contact between the parts to be coated and the conveyor can cause an electrical potential change and result in unevenly coated parts and a waste of coating material. This can occur because the charged coating material, which should migrate along electric field lines from the high potential dispensing device to the different potential maintained on the parts, instead, migrates along field lines established between the dispensing device and other articles and surfaces in the vicinity of the dispensing device which are maintained at low-magnitude potential, such as the conveyor itself. Thus, many of the benefits associated with electromotive coating are lost if the parts to be coated are not properly grounded or synchronized at a particular potential to terminate the electrostatic field.
The need for easily cleaned and operationally efficient hangars that suspend parts to be coated from conveyors that convey the parts past or through coating dispensing equipment is well established. Several types of such equipment are known, for example, the devices illustrated and described in U.S. Pat. No. 4,450,954 and U.S. Patent Publication No. 2004/0154536, the disclosures of which are hereby incorporated by reference in their entirety.
There has been a long felt need in the art to provide a ground mechanism that is sufficiently robust to efficiently maintain ground or other different potential for a part during electromotive coating. In addition, there remains a need to provide a more stable and predictable connection between a hangar or other connection device and a part to be coated. The connection should be such that relative electrical potential between all apparatus, including connecting devices, parts, paint or fluid spray, coating equipment, bath, etc., could be maintained and reproduced with ease during manufacture.
According to some aspects of the disclosed subject matter, an assembly for electromotively coating a conductive plastic can include a conveyor and an electrically-conductive plastic part that is electrically and mechanically coupled with the conveyor.
According to another aspect of the disclosed subject matter, an assembly for electromotively coating a part can include a conveyor apparatus that has a track and a hangar configured to move along the track. The hangar can include a fastener, and a part that is to be coated can include an attachment structure configured to be electrically and mechanically coupled with the fastener of the hangar. At least one of the fastener and the attachment structure can be configured to impart forces against the other of the fastener and the attachment structure in at least a first direction and a second direction, wherein the first direction is different from the second direction.
According to yet another aspect of the disclosed subject matter, an electromotive coating system can include a conveyor apparatus that has a track and at least one hangar configured to move along the track, the hangar including a fastener that includes threads. At least one part to be coated can include an attachment structure configured as threads that are electrically and mechanically connected with the part (e.g., the threads can be integral with or at least adhered or attached to the part).
According to another aspect of the disclosed subject matter, a method for connecting a part to a conveyor for electromotive coating of the part can include providing a conveyor apparatus including a track and at least one hangar having a fastener and configured to move along the track. The method can also include providing at least one part to be coated, the part including an attachment structure configured to electrically and mechanically connect the part to the hangar. The method can further include connecting the part to the hangar by applying a first force between the part and the hangar that has a first directional vector, and applying a second force between the part and the hangar that has a second directional vector, wherein the first directional vector is different from the second directional vector.
In another aspect of the disclosed subject matter, an electromotive coating system can include an electromotive coating dispensing device, a substantially electrically grounded conveyor, and at least one electrically-conductive plastic part electrically and mechanically coupled with the grounded conveyor. The dispensing device can be configured to dispense coating such as a paint or other fluid.
In accordance with yet another aspect of the disclosed subject matter, a ground mechanism for coupling a conductive plastic part to a conveyor for conveyance through electromotively charged coating material is provided. The ground mechanism can include a boss extending from the part, the boss being configured to receive a fastener.
Still other features and characteristics of the disclosed subject matter will become apparent to those skilled in the art from a reading of the following detailed description of exemplary embodiments that constructed in accordance with principles of the disclosed subject matter, and taken in conjunction with the accompanying drawings.
The disclosed subject matter of the present application will now be described in more detail with reference to exemplary embodiments of the disclosed apparatus and method, given only by way of example, and with reference to the accompanying drawings, in which:
Referring to the drawing figures, like reference numerals designate identical or corresponding elements throughout the several figures.
As shown in
The grounding mechanism or attachment structure 124 can be configured as a boss 122 extending from the part 110. The boss 122 includes threads 126 configured to connect to a fastener 224 on the hangar 220. The connection between the boss 122 and the fastener 224 can be sized and shaped such that a force is exerted by the fastener 224 onto the part 110 in at least two orthogonal directions and possibly all three orthogonal directions, such as when the threads 126 of the attachment structure 124 lock with threads 226 of the hangar 220. The boss 122 can be integrally molded with the part 110 to form a single piece of unitary construction via injection molding or other molding techniques. In the alternative, the boss 122 can be machined into the part 110 depending on the specific geometry of the part 110 and boss 122 and coating requirements.
The boss 122 can be sized and structured to allow the fastener 224, such as, for example, a screw-type metal fastener 224 with threads 226, to engage the conductive plastic boss 122 by cutting into the boss 122. The boss 122 can include threads 126 or the boss 122 can simply be an opening in the part 110 that can be tapped when the fastener 224 is threaded into boss 122 (or into the part 110 itself without boss 122). With multiple threads 226 engaging the boss 122, the part 110 can be firmly coupled with a conveyor such that the part 110 can proceed through an electromotive coating process without deformation or electrical arching. The boss 122 can be provided to ensure adequate space for the threads 126 and 226 of the part 110 and hangar 220 to interlock with each other. However, if the geometry of the part 110 permits, threads 126 can be provided directly within the part 110 (via molding, machining, etc.) and no boss 122 is required.
Referring back to
The connection between the attachment structure 124 of the part 110 and the fastener 224 located on the hangar 220 is sufficiently robust to maintain a ground (or to maintain a constant electrical potential) of the part 110 through all forces encountered during the coating process and through the heat encountered during transfer through curing ovens. The positive connection also allows coating material to adhere to the part 110 in a substantially even manner and prevents accidental or unwanted electrical current discharges.
It should be appreciated that other types of positive connectors may be used in place of the screw-type fasteners 224/attachment structures 124 shown in
The above specific and exemplary embodiments can be modified and changed without departing from the spirit and scope of the invention. For example, the spring arms 261 can be shaped in a semicircle or in a non-symmetrical manner to provide additional and/or differently directed force vectors when the spring arms 261 connect to the posts 123. In addition, any of the above-described embodiments can utilize a single or a plurality of hangars 220 corresponding to each part 110 that is to be moved through the conveyor system. The fasteners 124 and attachment structures 224, such as threads 126, 226, can be integrally formed on the part 110 and the hangar 220, or separate structures that include threads can be attached, mounted on, or otherwise adhered to the hangar 220 or part 110. In addition, while the conveyor system is shown as having a hangar 220 that has wheels 242 that follow track 244, other structures can be used without departing from the spirit and scope of the disclosed subject matter. For example, a continuous belt track can be used with hangars 220 that are permanently connected to the belt or detachable from the belt. Alternatively, magnets can be used to attach the hangars 220 to the belt, ball bearings, or other track structures.
While the disclosed subject matter has been described in detail with reference to exemplary embodiments thereof, it will be apparent to one skilled in the art that various changes can be made, and equivalents employed, without departing from the scope of the disclosed subject matter. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed subject matter. It is intended that the specification and examples be considered as exemplary only.
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|JPS58146466A||Title not available|
|U.S. Classification||204/512, 204/202, 118/621, 204/623, 427/483, 205/137|
|International Classification||B05B5/025, C25D17/28, C25D13/12|
|Cooperative Classification||Y10T29/49945, B05B5/082|
|Oct 5, 2007||AS||Assignment|
Owner name: HONDA MOTOR CO., LTD., JAPAN
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:CROWLEY, CARMEN;CROYLE, THOMAS H.;FITZ, TODD;AND OTHERS;REEL/FRAME:019927/0897;SIGNING DATES FROM 20071001 TO 20071002
Owner name: HONDA MOTOR CO., LTD., JAPAN
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:CROWLEY, CARMEN;CROYLE, THOMAS H.;FITZ, TODD;AND OTHERS;SIGNING DATES FROM 20071001 TO 20071002;REEL/FRAME:019927/0897